Photolysis of chlordane and heptachlor under ultraviolet light and laboratory light on glass plates and plant leaf surface will be studied and the photolytic products will be characterized. Toxicity of these photoisomers and their parent cyclodienes to freshwater invertebrates (Daphnia spp) and fish (goldfish and bluegills) will be determined. The fate of these photoisomers and their parent cyclodienes in insects (cockroaches, houseflies), mammals (rats, rabbits) and fish (bluegills and cichlids) will involve their organ distribution, tissue accumulation, elimination and metabolism. The metabolities will be isolated, purified, and identified. The bioaccumulation and biomagnification and ecological-concentration of these photoisomers by aquatic organisms either exposed alone or in a model ecosystem will be studied. These studies will evaluate the possible health and ecological hazards related with biological magnification, ecological magnification and metabolism of these toxicants.